RE: Iridium Next flare

From: Chris Peat via Seesat-l <>
Date: Fri, 6 Jul 2018 09:30:34 +0200
Hi all,

I have been given a contact at Iridium who can hopefully provide some information about the control algorithms of the solar panels.


I have also been thinking more about the flare producing mechanism since yesterday, and it seems I might have been a bit too optimistic.


Firstly, I think we can rule out flares coming from the solar panels if they are maintained perpendicular to the Sun. In this case, sunlight will be reflected directly back towards the Sun and will not produce a flare on the ground.


Secondly, a reflection from the flat bottom surface is always going to happen when the satellite is low in the sky, otherwise the Earth will block the line of sight between Sun and satellite.


From Roger Mansfield's post:

"The solar arrays are capable of automatic sun-tracking to increase exposure and optimize power generation during the sunlit portion of the orbit."

This is interesting, but does not make it clear if one or two degrees of freedom are used.


Our best hope for reliable flare predictions is if the solar panels have only one degree of freedom, and I hope the Iridium contact person can clear this up. The other current unknown is how tightly the attitude is controlled. If there is a large tolerance of say 5 degrees, then making reliable predictions could be impossible.


Chris Peat



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